WASHINGTON — NASA’s SPHEREx space telescope observed infrared emissions from dust, water, organic molecules and carbon dioxide in the coma of interstellar comet 3I/ATLAS during a December 2025 observing campaign and saw the comet brighten significantly roughly two months after its late-October close pass of the Sun, according to NASA’s SPHEREx mission blog, NASA Photojournal, BBC Sky at Night Magazine, and PrimeTimer. Those mutually confirmed points anchor this report.
- SPHEREx’s December 2025 infrared observations detected emissions from dust, water, organic molecules and carbon dioxide in 3I/ATLAS’s coma.
- The comet brightened markedly about two months after its late-October 2025 perihelion, consistent with delayed heating driving activity.
Additional Details Reported
Mission scientists say the SPHEREx data identified specific organic molecules, including methanol, cyanide and methane, expanding the chemistry profile of the interstellar visitor (NASA SPHEREx blog; BBC Sky at Night Magazine).
The December observations showed a more active, diverse coma than earlier campaigns, with subsurface water ice and rocky material feeding the outflow as solar heat penetrated the nucleus (NASA SPHEREx blog; PrimeTimer).
3I/ATLAS is the third confirmed interstellar object detected passing through the solar system, first reported to the Minor Planet Center on July 1, 2025 by the NASA-funded ATLAS survey in Chile, and its hyperbolic trajectory signals an origin beyond the Sun’s gravitational family (NASA comet overview; PrimeTimer).
NASA’s Photojournal notes that SPHEREx can see the sky in 102 infrared colors, a capability that helps pinpoint gases and dust in cometary comae (NASA Photojournal).
The new results build on a formal research note released by the team describing the detection of organics and the post-perihelion brightening (research note).
Image Attribution ▾
Image credit: NASA/JPL-Caltech License: NASA images are generally public domain (U.S. government work). See https://www.nasa.gov/nasa-brand-center/images-and-media/ for usage guidelines. Source: https://science.nasa.gov/photojournal/nasas-spherex-examines-comet-3i-atlass-coma/ Direct image: https://assets.science.nasa.gov/content/dam/science/psd/photojournal/pia/pia26/pia26720/PIA26720_SPHEREx_3I_4panel_colorized.png/jcr:content/renditions/cq5dam.web.1280.1280.png Modifications: Cropped and resized to 1920×1080 (16:9).
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